1. Field of the Invention
The present invention relates to a fuel cell system, and more particularly, to a fuel cell system having high electricity conversion efficiency.
2. Description of the Related Art
In general, a fuel cell is a device that generates electricity by an electrochemical reaction between air and fuel (i.e., hydrogen, LNG, LPG or the like). Basically, fuel cells are power generation systems that decompose air, which contains hydrogen and oxygen, using an electrochemical reaction and convert electrons, generated from the decomposition process, directly into electrical energy.
Such fuel cells are drawing attention due to their generation of green alternative energy, in that only water (H2O) is created after power generation.
Unlike existing power generation technologies adopting combustion, steam generation and turbine driving processes, fuel cells generate electricity directly from fuels without using a combustion process, and accordingly create less noise and air pollutants. Therefore, fuel cells are considered to be both efficient and eco-friendly.
Fuel cells include a reformer that generates a hydrogen gas by reforming a hydrocarbon fuel such as alcohol, methane, butane, LNG and the like, and a fuel cell stack that generates electrical energy by a chemical reaction between hydrogen and oxygen.
Fuel cell batteries may be classified into various kinds, such as Polymer Electrolyte Membrane Fuel cells (PEMFC), Direct Methanol Fuel Cells (DMFC), Molten-Carbonate Fuel Cells (MCFC), Soil Oxide Fuel Cells (SOFC), according to the chemical composition of a stack and the kind of initial fuel used as a source of hydrogen supply.
In the case in which heat energy generated from a reformer and a fuel cell stack in a power generation system adopting fuel cells is mostly released to the outside, the electricity conversion efficiency of a fuel may be impaired. Herein, the electricity conversion efficiency refers to the efficiency of converting a fuel into electrical energy. For the purpose of preventing this efficiency impairment, a power generation system using fuel cells, according to the related art, employs a plurality of heat exchangers so as to recover waste heat.
However, in the case in which the power generation system using fuel cells includes a plurality of heat exchangers, complications in system configuration and undesirable pipe extensions occur, causing loss in pipes such as a pressure drop. Furthermore, according to the related art, different heat exchangers need to be used for waste heat from a reformer and a stack, or an additional power supplier or a heat storage device needs to be installed in order to use waste heat generated from the power generation system using fuel cells.
Of late, systems allowing waste heat from a power generation system using fuel cells to be reused for room heating or water heating have been being provided.